Ashford MP Damian Green abstained in a key vote on the government's plans to shake-up the adult care system as Prime Minister Boris Johnson saw another challenge to his authority.

While the government secured a majority, it was just 26, with 19 Conservative MPs defying their party's instructions to back the Health and Social Care Bill.

Mr Green, who chairs the all-party group on adult social care, said the government should publish an impact assessment.

The former cabinet minister, who was one of 68 Tories who either abstained or could not vote, later said it was unclear whether the alteration to the cap for care costs is fair.

He told BBC’s Newsnight: “The party wants to see a proper fair solution to social care that is fair around the country and in all areas of the country. And to put it as politely as I can, it’s not yet clear that this solution achieves that.”

The government was criticised after it published an amendment under which support payments from councils would not count towards the £86,000 limit on personal care costs.

Some believe this will disproportionately affect poorer families.

The reforms are among the government’s flagship policies and the Prime Minister said that he wanted to fix it ‘once and for all’ when he took office.

Under the plans, due to come in 2023, no one would pay more than £86,000 over their lifetime for personal care, such as washing, dressing and eating.

When the cap was reached, ongoing costs for care would be paid for by local authorities.

The vast majority of Kent's Conservative MPs backed the changes, although Maidstone and the Weald's Helen Grant, Tonbridge and Malling's Tom Tugendhat and Dartford's Adam Holloway either abstained or were not present to vote.

The Bill will now go to the Lords for debate before returning to the Commons.

ANALYSIS

While the government survived in last night's vote on its long-awaited overhaul all of the adult care system, the rebellion by a small number of Conservative backbenchers was another challenge to the Prime Minister’s authority.

Coming after the cancellation of part of the plans for High Speed 2 and yesterday's erratic speech to business chiefs, there are some who believe that the Prime Minister is losing his grip.

It is way too early to speculate on the possibility of him being ditched but last night’s vote ought to sound alarm bells in Downing Street.

After all, reform of the adult care system is a cornerstone policy commitment.

The fact that it has run into trouble and is being criticised for having a disproportionate impact on poorer families does not bode well for the Prime Minister.